1. Field of Invention
The invention relates to a holding device for a rim of a vehicle wheel, preferably for pressing the rim onto a bearing flange of a shaft of a balancing machine, said holding device having a base plate which has a central recess for being pushed onto the shaft of the balancing machine, having a plurality of rotatably mounted holding elements, which are arranged preferably at a uniform mutual circumferential spacing and preferably at a uniform radial spacing from the central recess, and having at least one coupling element which is arranged coaxially with respect to the central recess and is mounted rotatably on the base plate, the holding elements and the coupling element having interacting coupling means for the positive coupling of the rotational movement of the holding elements, and each holding element having a holding means which is preferably mounted eccentrically.
2. Description of Related Art
U.S. Pat. No. 4,167,118 has already disclosed an apparatus having a base plate which has a central recess for being pushed onto the shaft of a balancing machine, having a plurality of rotatably mounted holding elements and having at least one coupling element which is arranged coaxially with respect to the central recess and is mounted rotatably on the base plate, the holding elements and the coupling element having interacting coupling means for the positive coupling of the rotational movement of the holding elements, and each holding element having a holding means for the rim of a vehicle wheel. For the positive coupling of the rotational movement of the holding elements, the known apparatus has, in each case, coupling pins on the rotatably mounted holding elements, which coupling pins engage in each case into radial slots of a coupling element of annular configuration which is arranged on a base plate and can be rotated about the axis of a central recess in the base plate. By rotation of the coupling element, the coupling pins are driven and therefore the holding elements are rotated about their rotational axis. During rotation of the holding elements, the radial spacing of pressure pins which are mounted eccentrically on the holding elements changes with respect to the axis of the central recess of the base plate, and the mutual circumferential spacing of the pressure pins also changes. As a result, it is possible to adapt the radial spacing of the pressure pins of the central recess and the mutual circumferential spacing of the pressure pins as a function of the pitch circle diameter of fastening holes of a rim of a vehicle wheel which is to be balanced.
While the known apparatus is being pushed onto a shaft of a balancing machine and being pressed onto the rim of the vehicle wheel, the pressure pins engage on the end side into fastening holes of the rim, with the result that the rim is pressed firmly against the bearing flange during clamping of the apparatus against the bearing flange of the balancing machine. Since the clamping forces are transmitted to the fastening holes of the rim only by the ends of the pressure pins, no other parts of the surface of the rim can be damaged by the pressure pins, which is advantageous not only in the case of painted steel rims, but also, in particular, in the case of rims made from anodized lightweight metal, for example aluminum.
It is a disadvantage of the apparatus which is known from U.S. Pat. No. 4,167,118 that the positive coupling of the rotational movement of the holding elements is not possible without play on account of tolerances during manufacture. This has the consequence that exact maintenance of the mutual circumferential spacing of the pressure pins and also of their radial position with respect to the shaft of a balancing machine is not ensured, with the result that unbalance errors which lead to faulty balancing of the vehicle wheel can occur during the balancing operation as a result of the known apparatus.
U.S. Pat. No. 4,070,915 has disclosed a holding device for a rim of a vehicle wheel, in which holding device the rim is fastened directly to the device. The known device has a base plate with a plurality of holding elements, which are arranged at a uniform mutual circumferential spacing and at a uniform radial spacing from a central recess of the base plate and are mounted on the base plate, each holding element having an eccentrically mounted threaded bolt for fastening the rim to the device. A gearwheel which is arranged coaxially with respect to the central recess of the base plate and is mounted rotatably on the base plate is provided for the positive coupling of the rotational movement of the holding elements. The gearwheel is toothed in sections on its circumferential face, the toothed sections of the gearwheel meshing with toothed sections of the holding elements. It is possible by rotation of the gearwheel to adjust the radial spacing of the threaded bolts from the central recess of the base plate and to adjust the mutual circumferential spacing of the threaded bolts. The known device likewise has the disadvantage that the transmission of the movement between the meshing toothing sections is not possible without play. This in turn has the consequence that exact maintenance of the mutual circumferential spacings of the threaded bolts and also of their radial position with respect to the shaft of the balancing machine is not ensured, with the result that unbalance errors can occur during the balancing operation as a result of the device.
German Patent Application DE 26 19 618 A1 has disclosed a wheel holder for a wheel balancing or a tire changing machine having a carrier plate which is mounted rotatably and serves to receive a rim of a wheel. Satellite gears are mounted rotatably on the carrier plate at a uniform radial spacing from the rotational axis of the carrier plate, a central gear group being provided for coupling the rotational movement of the satellite gears. The central gear group meshes with all the satellite gears. If one of the satellite gears is rotated, wheel fastening bolts which are arranged eccentrically on the satellite gears are displaced via the central gear group to circles which are concentric with respect to the rotational axis of the carrier plate. A force can be exerted on the central gear group, by which force the central group is spread radially with respect to the rotational axis of the carrier plate, in order to bring its teeth into full engagement with the teeth of the satellite gears. It is possible as a result to reduce the play between the teeth of the central gear group and the teeth of the satellite gears, without impairing the rotational movement of the gearwheels. However, the known wheel holder is of structurally complicated design, which increases the expenditure for assembly and the manufacturing costs. Otherwise, it has been shown in practice that the exertion of force on the central gear group can lead to the teeth of the central gear group jamming between the teeth of the satellite gears. A rotational movement of the gearwheels is then no longer possible.
German Patent DE-C 1 195 071 has disclosed a device for clamping vehicle wheels in a centered manner on a disk which is mounted rotatably on a carrying axle by way of planetary gears which are carried by said disk. Carrying bolts which are mounted eccentrically on the planetary gears are provided for fastening to the rim. The planetary gears can be adjusted by a sun gear which is arranged on the carrying axle, the sun gear being configured as a friction wheel which drives the planetary gears. The carrying bolts can be adjusted uniformly by rotation of the sun gear, the relatively constant spacing of the carrying bolts being maintained substantially and the annular ring diameter changing uniformly for all carrying bolts. Here, each planetary gear is rotated independently of the other planetary gears until the carrying bolt which is influenced by it has reached an alignment end position. As a result, the known device is intended to ensure that the wheel to be tested is held by all carrying bolts in the precise alignment position with respect to the balancing axis of the balancing machine. The above-described device has the disadvantage that the frictional coupling of the rotational movement of the holding elements is associated with increased wear, which leads to it being necessary for the sun gear to be replaced at short time intervals in the known device. This contributes to high maintenance costs of the known device. In addition, slipping of the planetary gears can occur, which can lead to undesired displacement of the carrying bolts.